1. Field of the Invention
The present invention is related to a radio-frequency circuit for a wireless signal transceiver and related wireless signal transceiver, and more particularly, to a radio-frequency circuit and related wireless signal transceiver for ensuring the efficiency of antenna to avoid mutual interference of wireless signals.
2. Description of the Prior Art
Satellite Radio is a 3rd generation broadcasting technique following Amplitude Modulation (AM) and Frequency Modulation (FM) broadcasting techniques. The satellite radio technique solves the lack of available broadcasting channels with better spectral utilization efficiency. Moreover, CD-like sound quality and supplementary digital data service fit the diversification of broadcasting media. Therefore, the analog broadcasting system tends to be replaced by the satellite radio system.
Techniques utilized by the satellite radio system, such as modulation and coding, are greatly different from those utilized by the conventional AM and FM broadcasting systems. Hence, the conventional AM and FM demodulators, such as radio players, cannot be used in the satellite radio system. In other words, a user needs to purchase a satellite radio demodulator for receiving digital broadcasting programs. However, a vehicle multimedia system is integrated with a vehicle housing or interior, such that the user cannot receive the satellite radio programs in a car by replacing a satellite radio demodulator, causing inconvenience.
In consequence, the prior art has provided a vehicle satellite radio receiver, which is compatible with the vehicle FM demodulator, and combines a satellite radio demodulator and a FM transmitter, for transforming satellite radio signals into FM signals for the vehicle FM demodulator, allowing the user to play the satellite radio programs via a vehicle audio system. For example, please refer to FIG. 1. FIG. 1 is a schematic diagram of a vehicle satellite radio receiver 10 in the prior art. The vehicle satellite radio receiver 10 comprises a satellite reception antenna 100, a satellite radio demodulation module 102, an audio signal processing module 104, a FM modulation module 106, and a FM transmission antenna 108. Satellite radio signal is received by the satellite reception antenna 100 and transformed into baseband audio signal for the audio signal processing module 104 via the satellite demodulation module 102. The audio signal processing module 104 can send out the satellite radio content via a connected speaker or headset (not shown in FIG. 1). Or, the satellite radio content can also be transformed into FM signal by the FM modulation module 106 and emitting into the air through the transmission antenna 108. In other words, the vehicle satellite radio receiver 10 can emit the satellite radio content to the vehicle FM demodulator in the form of FM signal, allowing the user to receive the satellite radio programs without replacing the original vehicle multimedia system.
Consequently, the user can listen to the satellite radio programs by the vehicle satellite radio receiver 10 instead of replacing the original vehicle multimedia system. However, as shown in FIG. 1, the vehicle satellite radio receiver 10 needs at least two transmission lines L_1 and L_2 to transfer satellite signal and FM signal respectively. Such design is not neat and may easily cause inconvenience for the user. If the transmission lines L_1 and L_2 are fixed or tied together, the effect of FM transmission might be affected. The main reason is, the communication administration (e.g. Federal Communications Commission, FCC) in every country makes rules on the radiation power of FM channels. Under the circumstances of the confined radiation power, the FM signal emitted by the FM transmission antenna 108 is easily interfered, so that the transmission line L_1 and L2 cannot be fixed or tied together.
In short, the common vehicle satellite radio reception needs at least two transmission lines to transmit the satellite signal and the FM signal, easily causing a messy condition and inconvenience for the user.